Generally speaking, the present invention relates to antennas for portable telecommunication apparatuses, such as mobile telephones. More particularly, the invention relates to a multi-band antenna, comprising a pattern of thin conductive material, which is adapted to operate in a least two frequency bands.
A portable telecommunication apparatus, such as a mobile telephone, requires some form of antenna in order to establish and maintain a wireless radiolink to another unit in the telecommunications system, normally a radio base station. Some years ago, many mobile telephones were provided with retractable whip antennas or non-retractable stub or helix antennas. More recently, other antenna types have been developed, which comprise a pattern of thin conductive material, usually copper, that is printed on a flexible dielectric substrate and is mounted on a suitable portion of the mobile telephone.
WO99/25043 discloses an antenna, which comprises a printed pattern of conductive material to be mounted on a flip, that is pivotally mounted to the main apparatus housing of the telephone. The printed antenna pattern comprises a meander-shaped portion, which acts as the actual antenna, and a spiral-shaped portion, which acts as an impedance matching network. On an opposite side of the flip a ground patch element is provided in alignment with the spiral-shaped impedance matching portion of the printed pattern.
EP-A2-0 923 158 discloses a dual-band antenna of a similar type. A radiating element with a meander form is printed on a first surface of a dielectric plate. On an opposite surface of the dielectric plate there is provided a planar parasitic element, which in some embodiments may operate as a separate radiator, thereby providing the antenna with the ability of operating in three frequency ranges. The antenna of EP-A2-0 923 158 is particularly adapted for mounting on the back wall of a mobile telephone.
It is a primary object of the present invention to provide a substantial improvement over previously known antennas of the type having a pattern of thin conductive material and being adapted to operate in more than one frequency band. More specifically, it is an object of the invention to provide an antenna, which is small, flexible and has good performance not only in a low frequency band, such as the 900 MHz GSM band, but also good performance in higher frequency bands, such as the 1800 MHz GSM or DCS band as well as the 1900 MHz GSM or PCS band.
An additional object is to provide an antenna, which may be formed as an integral pattern of conductive material, arranged in essentially a single plane, without requiring a separate parasitic or patch element for impedance matching purposes.
Still an object of the invention is to provide an antenna, which does not require a well-defined electrical ground.
Yet another object is to provide an antenna, which i inexpensive to manufacture.
Finally, another object is to provide an antenna, which may be embedded in a flexible plastic or rubber coating, which may be attached to an external portion of the mobile telephone and which may be bent, within reasonable limits, without damaging the antenna.
The objects above are achieved by a multi-band antenna according to the attached independent claim. More specifically, the objects are achieved for a multi-band antenna of the type comprising a pattern of thin conductive material, which is adapted to operate in at least two, preferably at least three, frequency bands, by the provision of a first portion of conductive material adapted to be connected to radio circuitry in a portable telecommunication apparatus, and a second portion of conductive material, which is connected to the first portion of conductive material, has a non-linear extension and is narrower than the first portion.
According to a preferred embodiment, the above objects are moreover achieved by providing the multi-antenna with a third portion of conductive material, which is connected to the second portion, is wider than the second portion and provides capacitive loading of the antenna.
Other objects, features and advantages of the present invention will appear from the following detailed disclosure of preferred and alternative embodiments, from the enclosed drawings as well as from the subclaims.